How do the thickness and density of continental crust differ from oceanic crust?

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World map highlighting major features of the ocean basins, including trenches, ridges, basins, and plateaus labeled throughout the Pacific, Atlantic, Indian, Southern, and Arctic Oceans. Continents are shown with shaded terrain, and prominent undersea features such as the Mid-Atlantic Ridge, Mariana Trench, and Kerguelen Plateau are marked across the map. — ocean basin Major features of the ocean basins.

The continental and oceanic crusts differ significantly in both thickness and density, which fundamentally shapes the topography of Earth.

Density

Continental crust is primarily granitic in composition and has a density of approximately 2.7 grams per cubic cm. In contrast, oceanic crust is basaltic—richer in iron and magnesium—resulting in a higher density of about 2.9 to 3 grams per cubic cm. Because the continental crust is less dense, it possesses greater buoyancy, allowing it to float higher in the mantle compared to the denser oceanic crust.1

Thickness

There is a marked difference in the physical dimensions of these two layers:
* Continental Crust: Typically reaches a thickness of about 40 km (25 miles).1
* Oceanic Crust: Is much thinner, averaging approximately 6 km (4 miles) in thickness.1

This disparity in density and thickness is responsible for the two principal levels of Earth's surface, with continents standing well above sea level while ocean basins sit at an average depth of 3,790 metres (12,400 feet).1